1. Field of the Invention
The present invention relates to an apparatus for extracting pitch data from an input waveform signal and an electronic system of a type for generating a musical tone having a pitch corresponding to extracted pitch data and, more particularly, to an electronic stringed instrument such as an electronic guitar or a guitar synthesizer.
2. Description of the Related Art
In recent years, various types of electronic systems have been developed to extract pitch (fundamental frequency) data from a waveform signal generated in accordance with human varies and/or tones of acoustic musical instruments and to control a sound source constituted by an electronic circuit so as to artificially obtain an acoustic effect such as a musical tone.
The following prior arts disclose the above technique:
U.S. Pat. No. 4,117,757 (issued on Oct. 3, 1978), inventor: Akamatsu,
U.S. Pat. No. 4,606,255 (issued on Aug. 19, 1986), inventors: Hayashi et al.,
U.S. Pat. No. 4,633,748 (issued on Jan. 6, 1987), inventors: Takashima et al.,
U.S. Pat. No. 4,688,464 (issued on Aug. 25, 1987), inventors: Gibson et al.,
Japanese Patent Publication No. 57-37074 (published on Aug. 7, 1982), applicant: Roland Kabushiki Kaisha,
Japanese Patent Publication No. 57-58672 (published on Dec. 10, 1982), applicant: Roland Kabushiki Kaisha,
Japanese Patent Disclosure (Kokai) No. 55-55398 (disclosed on Apr. 23, 1980), applicant: TOSHIBA CORP.,
Japanese Patent Disclosure (Kokai) No. 55-87196 (disclosed on July 1, 1980), applicant: Nippon Gakki Co., Ltd.,
Japanese Patent Disclosure (Kokai) No. 55-159495 (disclosed on Dec. 11, 1980), applicant: Nippon Gakki Co., Ltd.,
Japanese Utility Model Disclosure (Kokai) No. 55-152597 (disclosed on Nov. 4, 1980), applicant: Nippon Gakki Co., Ltd.,
Japanese Utility Model Disclosure (Kokai) No. 55-162132 (disclosed on Nov. 20, 1980) applicant: Keio Giken Kogyo Kabushiki Kaisha,
Japanese Patent Publication No. 61-51793 (published on Nov. 16, 1986), applicant: Nippon Gakki Co., Ltd., and
Japanese Utility Model Publication No. 62-20871 (published on May 27, 1987), applicant: Fuji Roland Kabushiki Kaisha.
U.S. patent application disclosing a system relating to the present invention was filed by Uchiyama et al. as U.S. Ser. No. 112,780 on Oct. 22, 1987.
In these prior arts, in order to extract pitch data from an input waveform signal, a time interval between two positive peaks, between negative peaks, or between zero-crossings immediately after these peaks of the input waveform signal is measured. A circuit for detecting a peak is generally exemplified by an analog circuit including capacitors and resistors. It is often difficult to perform good peak detection of the input waveform signal of the musical instrument due to variations in circuit components, durability, and deteriorations over time. The peak detector comprises an analog system which requires a large number of circuit components, resulting in high cost. It is also inconvenient to realize easy element mounting. In particular, in an electronic musical instrument incorporating a sound source circuit, a mounting space must be minimized. In a conventional circuit arrangement, it is impossible or is very difficult to obtain a mounting space. When condition parameters are to be changed for pitch extraction, special circuits must be prepared every time the parameters are changed. Therefore, it is very difficult to change such parameters.